The present invention relates to an EDM process and apparatus wherein the electrodes, electrode workpiece and electrode tool, are displaced relative to each other during machining by electrical discharges, in a slant direction, or a direction at an angle to the principal axis of feed of one electrode relative to the other.
In U.S. Pat. No. 4,135,070, assigned to the same assignee as the present application, there is disclosed a process and apparatus presenting the advantage of machining simultaneously a lateral surface and a frontal surface of an electrode workpiece, as a result of providing a slanted feed of one electrode relative to the other, and providing simultaneous withdrawal of the electrode tool from proximate the machined surfaces in the event of a short circuit, for example.
Such an arrangement permits to obtain a uniform multi-directional quasi-enlargement of the electrode tool, if the position limits of the displacement in every direction of one electrode relative to the other have a hemispherical envelope. As disclosed in said patent, the relative displacements in the slant directions are effected successively in the same direction along the principal axis of relative feed of the electrodes.
The principal object of the invention is to improve upon the method disclosed in the aforementioned patent, while preserving all of its advantages. The present invention contemplates that the slant direction of electrode relative feed in the course of a first machining pass is arbitrarily chosen such as to produce electrical discharges machining alternatively of the lateral surfaces and of the frontal surfaces of the workpiece, and for a variation of the slant direction in the course of subsequent machining passes such as to machine consecutively the lateral and frontal surfaces of the workpiece, and further provides for the speed of feed of the electrode tool into the workpiece to be maintained within predetermined limits in the course of each of the machining passes.
When the speed of feed does not vary as a function of the surface being machined, the mentioned sequence of machining passes permits to obtain a substantial reduction of the duration of a machining operation.
The various objects and advantages of the present invention will become apparent to those skilled in the art from the following description of the best mode contemplated for practicing the invention, when read in conjunction with the accompanying drawing showing, for illustrative purposes only, two examples of structure for practicing the invention, and in which: